Bidirectional operation of wireless power systems

ABSTRACT

Described herein are active rectification methods and systems for a rectifier of a wireless power system. Exemplary methods can include detecting, by a zero-crossing detector, one or more zero-crossings of a current at an input of the rectifier and determining a first delay time based on at least one wireless power system parameter and the zero-crossings. The methods can include generating first and second control signals for first and second switches of the rectifier, respectively, based on the first delay time; inserting a first dead time between the first control signal and the second control signal; and providing the first and second control signals to the first and second switches, respectively.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/003,800 titled “CONTROL OF ACTIVE RECTIFICATION IN WIRELESS POWERSYSTEMS” and filed on Aug. 26, 2020, which claims priority to and thebenefit of U.S. Provisional Patent Application No. 62/891,959 titled“CONTROL OF ACTIVE RECTIFIER SWITCHES IN WIRELESS POWER SYSTEMS” andfiled on Aug. 26, 2019, the entire contents of each of which are herebyincorporated by reference herein.

TECHNICAL FIELD

The following disclosure is directed to active rectification methods andsystems in wireless power systems and, more specifically, control ofactive rectification methods and systems in wireless power receivers.

BACKGROUND

Wireless power systems are configured to transmit power to a load (e.g.,a battery of an electrical device) without mechanical contact betweenthe transmitter and receiver. Wireless power receivers of such systemsgenerally include a rectifier to convert oscillating energy to DC fordelivery to a load (e.g., a battery) coupled to the receiver. It can bebeneficial for the rectifier to operate with high efficiency.

SUMMARY

Disclosed herein are active rectification control methods for wirelesspower systems.

In one aspect, the disclosure features an active rectification methodfor a rectifier of a wireless power system. The method can includedetecting, by a zero-crossing detector, one or more zero-crossings of acurrent at an input of the rectifier; and determining a first delay timebased on at least one wireless power system parameter and thezero-crossings. The method can further include generating first andsecond control signals for first and second switches of the rectifier,respectively, based on the first delay time; inserting a first dead timebetween the first control signal and the second control signal; andproviding the first and second control signals to the first and secondswitches, respectively.

Various embodiments of the active rectification method can include oneor more of the following features. The method can include determining asecond delay time based on the wireless power system parameter and thezero-crossings; generating third and fourth control signals for thirdand fourth switches of the rectifier, respectively, based on the seconddelay time; inserting a second dead time between the third controlsignal and the fourth control signal; and providing the third and fourthcontrol signals to the third and fourth rectifier switches,respectively. The third and fourth switches can be coupled to the firstand second switches in a full-bridge configuration. The rectifier can bepart of a wireless power receiver. The rectifier can be part of awireless power transmitter.

The rectifier can include two diodes coupled in a full-bridge rectifierconfiguration with the first and second switches. The first and secondswitches can be low-side switches of the rectifier. The first and secondswitches can be coupled to a first rectifier input and the two diodesare coupled to a second rectifier input. The first delay time can bedetermined by a delay block operably coupled to the zero-crossingdetector. The zero-crossings can include a first zero-crossingcorresponding to a rise in the current and a second zero-crossingcorresponding to a fall in the current. A value of the at least onewireless power system parameter can be based on at least one of: (i) animpedance of the rectifier; (ii) a power level transmitted to a loadcoupled to the wireless power system; or (iii) a coil current of awireless power receiver comprising the rectifier.

In another aspect, the disclosure features an active rectificationsystem for a wireless power system. The system can include a firstswitch and a second switch coupled between a source of oscillatingcurrent and a battery of the wireless power system; and a control systemcoupled to each of the first switch and the second switch. The controlsystem can be configured to: detect one or more zero-crossings of theoscillating current at an input of the rectifier; and determine a firstdelay time based on at least one wireless power system parameter and thezero-crossings. The control system can be further configured to:generate first and second control signals for the first and secondswitches of the rectifier, respectively, based on the first delay time;insert a first dead time between the first control signal and the secondcontrol signal; and provide the first and second control signals to thefirst and second switches, respectively.

Various embodiments of the active rectification system can include oneor more of the following features. The system can include a third switchand a fourth switch coupled between the source of oscillating currentand the battery of the wireless power system. The control system can befurther configured to: determine a second delay time based on thewireless power system parameter and the zero-crossings and generatethird and fourth control signals for third and fourth switches of therectifier, respectively, based on the second delay time. The controlsystem can be further configured to insert a second dead time betweenthe third control signal and the fourth control signal; and provide thethird and fourth control signals to the third and fourth rectifierswitches, respectively. The third and fourth switches can be coupled tothe first and second switches is a full-bridge configuration.

The rectifier can be part of a wireless power receiver. The rectifiercan be part of a wireless power transmitter. The rectifier can includetwo diodes coupled in a full-bridge rectifier configuration with thefirst and second switches. The first and second switches can be low-sideswitches of the rectifier. A value of the at least one wireless powersystem parameter can be based on at least one of: (i) an impedance ofthe rectifier; (ii) a power level transmitted to the battery coupled tothe wireless power system; or (iii) a coil current of a wireless powerreceiver comprising the rectifier.

In another aspect, the disclosure features an active rectificationmethod for a wireless power system. The method can include detecting, bya zero-crossing detector, one or more zero-crossings of a current at aninput of the rectifier; generating a phase lock loop (PLL) signal basedon the rising zero-crossing and falling zero-crossing; determining afirst delay time based on at least one wireless power system parameterand the zero-crossings; generating first and second control signals forfirst and second switches of the rectifier, respectively, based on thefirst delay time and PLL signal; inserting a first dead time between thefirst control signal and the second control signal; and providing thefirst and second control signals to the first and second switches,respectively.

In another aspect, the disclosure features an active rectificationmethod for a wireless power system. The method can include receivingand/or filtering a current at an input of the rectifier; detecting, by azero-crossing detector, one or more zero-crossings of a current at aninput of the rectifier; determining a first delay time based on at leastone wireless power system parameter and the zero-crossings; generatingfirst and second control signals for first and second switches of therectifier, respectively, based on the first delay time; inserting afirst dead time between the first control signal and the second controlsignal; and providing the first and second control signals to the firstand second switches, respectively.

In another aspect, the disclosure features an active rectificationmethod for a wireless power system. The method can include detecting, bya zero-crossing detector, one or more zero-crossings of a current at aninput of the rectifier; generating a phase lock loop (PLL) signal basedon the rising zero-crossing and falling zero-crossing; determining afirst voltage signal based on one or more wireless power systemparameters; generating first and second control signals for first andsecond switches of the rectifier, respectively, based on the PLL signaland the first voltage signal; inserting a first dead time between thefirst control signal and the second control signal; and providing thefirst and second control signals to the first and second switches,respectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an exemplary wireless power system.

FIG. 2A is a schematic of an exemplary wireless power system employingactive rectification.

FIGS. 2B-2C are schematics of exemplary wireless power receiversemploying active rectification.

FIG. 3A is a schematic of an exemplary wireless power system employingactive rectification.

FIG. 3B is a diagram of an exemplary workflow for determining controlsignals for rectifier switches based on the input current.

FIG. 3C is a set of plots illustrating various signals in the generationof the control signals as a function of time.

FIG. 3D is a flowchart of an exemplary method for rectifier switchcontrol in a wireless power system.

FIG. 4A is a diagram of an exemplary workflow \ for determining controlsignals for rectifier switches based on input current.

FIG. 4B is a set of plots illustrating various signals in the generationof the control signals as a function of time.

FIG. 4C is a flowchart of an exemplary method for rectifier switchcontrol in a wireless power system.

FIG. 5A is a diagram of an exemplary workflow for generating controlsignals for rectifier switches based on input current.

FIG. 5B is a set of plots illustrating various signals in the generationof the control signals as a function of time.

FIG. 5C is a flowchart of an exemplary method for rectifier switchcontrol in a wireless power system.

FIG. 6A is a diagram of an exemplary workflow for determining controlsignals for rectifier switches based on input current and input voltage.

FIG. 6B is a set of plots illustrating various signals in the generationof the control signals as a function of time.

FIG. 6C is a flowchart of an exemplary method for rectifier switchcontrol in a wireless power system.

FIG. 6D is a flowchart of a method for generating control signalsaccording to the workflow of FIG. 6A.

FIG. 7 is a schematic of an exemplary bidirectional wireless powertransfer system.

FIG. 8 is a flowchart of an exemplary bidirectional control process.

FIG. 9 is a schematic of an exemplary inverter-rectifier and a timingdiagram illustrating operation of the inverter-rectifier in an inverteroperating mode.

FIG. 10 is a schematic of an exemplary inverter-rectifier and a timingdiagram illustrating operation of the inverter-rectifier in a rectifieroperating mode.

FIG. 11 is a block diagram of an example computer system that may beused in implementing the active rectification systems and methodsdescribed herein.

DETAILED DESCRIPTION

Disclosed herein are exemplary embodiments of active rectificationsystems and methods in wireless power systems. Specifically, activerectification can be used in wireless power receivers. Activerectification employs actively controlled switches coupled so as to forma rectifier. Switches can include transistors (e.g., FETs, MOSFETs,BJTs, IGBTs, etc.). In an exemplary wireless power system, an activerectifier can be used to convert oscillating current (AC) received atthe wireless power receiver to direct current (DC), which can be used toultimately transfer energy to a load, as described further below.Details of illustrative embodiments are discussed below.

Wireless Power System Overview

FIG. 1 is a block diagram of an exemplary wireless power system 100. Thesystem 100 includes a wireless power transmitter 102 and a wirelesspower receiver 104. In transmitter 104, a power source (e.g., AC mains,battery, etc.) provides power to an inverter 108. Additional componentscan include power factor correction (PFC) circuit 106 before theinverter stage 108. The inverter 108 drives the transmitter resonatorcoil and capacitive components 112 (“resonator”), via an impedancematching network 110 (including fixed and/or tunable networkcomponents). The transmitter resonator 112 produces an oscillatingmagnetic field which induces a voltage and/or current in receiverresonator 114. The received energy is provided to a rectifier 118 viaimpedance matching network 116 (including fixed and/or tunable networkcomponents). Ultimately, the rectified power is provided to a load 120(e.g., one or more batteries of an electric or hybrid vehicle). In someembodiments, the battery voltage level can impact various parameters(e.g., impedance) of the wireless power system 100. Therefore, thebattery voltage level may be received, determined, or measured to beprovided as input to other portions of the wireless power system 100.For example, typical battery voltage ranges for electric vehiclesinclude 200-280 V, 200-350 V, 200-420 V, etc.

In some embodiments, one or more components of the transmitter 102 canbe coupled to a controller 122, which may include a communication module(e.g., Wi-Fi, radio, Bluetooth, in-band signaling mechanism, etc.)configured to communicate with a communication module of receiver 104.In some embodiments, one or more components of the transmitter 102 canbe coupled to one or more sensors 124 (e.g., a current sensor, a voltagesensor, a power sensor, a temperature sensor, a fault sensor, etc.). Thecontroller 122 and sensor(s) 124 can be operably coupled to controlportions of the transmitter 102 based on feedback signals from thesensor(s) 124 and/or sensor(s) 128.

In some embodiments, one or more components of the receiver 104 can becoupled to a controller 126, which may include a communication module(e.g., Wi-Fi, radio, Bluetooth, in-band signaling mechanism, etc.)configured to communicate with a communication module of transmitter102. In some embodiments, one or more components of the transmitter 104can be coupled to one or more sensors 128 (e.g., a current sensor, avoltage sensor, a power sensor, a temperature sensor, a fault sensor,etc.). The controller 126 and sensor(s) 128 can be operably coupled tocontrol portions of the transmitter 102 based on feedback signals fromthe sensor(s) 128 and/or sensor(s) 124.

Examples of wireless power systems can be found in U.S. PatentApplication Publication No. 2010/0141042, published Jun. 10, 2010 andtitled “Wireless energy transfer systems,” and U.S. Patent ApplicationPublication No. 2012/0112535, published May 10, 2012 and titled“Wireless energy transfer for vehicles,” both of which are herebyincorporated by reference in their entireties.

The exemplary systems and methods disclosed herein may be described withrespect to a vehicle application but can also be applied to any systemor apparatus powered by electricity, e.g., robots, industrial machines,appliances, consumer electronics, etc. High-power wireless powertransmitters can be configured to transmit wireless power inapplications such as powering of and/or charging a battery of vehicles,industrial machines, robots, or electronic devices relying on highpower. For the purpose of illustration, the following disclosure focuseson wireless power transmission for vehicles. However, it is understoodthat any one or more of the embodiments described herein can be appliedto other applications in which wireless power can be utilized.

As used herein, the term “capacitor”, or the symbol therefor, can referto one or more electrical components having a capacitance (e.g., inFarads) and/or capacitive reactance (e.g., in Ohms). For example, acapacitor may refer to one or more capacitors (e.g., in a “bank” ofcapacitors) that may be on the order of tens, hundreds, etc. of discretecapacitors. Two or more capacitors may be coupled in series or parallelto attain the desired capacitance and/or desired capacitive reactance.Note that capacitive reactance may be expressed as a negative valueherein. However, one skilled in the art would recognize that, in someconventions, capacitive reactance may also be expressed as a positivevalue.

As used herein, the term “inductor”, or the symbol therefor, can referto one or more electrical components having a inductance (e.g., inHenries) and/or inductive reactance (e.g., in Ohms). For example, aninductor may refer to one or more discrete inductors or coils. Two ormore inductors may be coupled in series or parallel to attain a desiredinductance and/or desired inductive reactance. Note that inductivereactance may be expressed as a positive value herein.

While the disclosure, including the Figures, may provide exemplaryvalues for the various electrical components, it is understood that thevalue of the components can be customized for the particularapplication. For example, the value of various electronic components candepend whether the wireless power transmitter is used to transmit powerfor charging a vehicle battery (on the order of thousands of Watts) or acell phone battery (typically less than 5 Watts).

Active Rectification in Wireless Power Receivers

In some embodiments, active rectification can enable a greater degree ofcontrol over power transmission to the output of the receiver 104 and/orload 120. In some embodiments, active rectification can enable moreefficient power transmission to the output of the receiver 104 and/orload 120. In some embodiments, by employing active rectification in awireless power receiver, the tunable impedance matching components inthe receiver 104 and/or transmitter 102 can be eliminated. This can havethe benefit of reducing the size, weight, and/or cost associated withthe wireless power system.

FIG. 2A is a schematic of an exemplary wireless power system 200leveraging active rectification. The exemplary system 200 includes awireless power transmitter 202. The exemplary transmitter 202 includesan inverter 206 (e.g., a half-bridge inverter, a full-bridge inverter,etc.) coupled to a filter circuit 207 (which can include, e.g., one ormore inductive components L3 sA, L3 sB, one or more capacitivecomponents, etc.). The inverter 206 can include two or more switches(e.g., transistors Q1, Q2, Q3, and Q4). The switches Q1, Q2, Q3, Q4 canbe controlled via respective control signals PWM1, PWM2, PWM3, PWM4. Thefilter 207 can be further coupled to a transmitting resonator and/ormatching circuit 208 (including capacitors C2 s, C1 sA, C1 sB, andinductor L1 s), as described above.

In exemplary system 200, the inductor L1 s of circuit 208 can beinductively coupled to the inductor L1 d of receiving resonator and/ormatching circuit 210 (including capacitors C1 dA, C1 dB, C2 d, andinductor L1 d) so as to wirelessly transmit power from the transmitter202 to the receiver 204 a. Note that the transmitter coil L1 s generatesan oscillating magnetic field, which can induce an oscillating currentat the receiver coil L1 d. This current can have a frequency of, forexample, 85 kHz. In many instances, the current I3 d can includeharmonics due to the inverter 206. In some embodiments, characteristics(e.g., phase, amplitude, shape, harmonic content, etc.) of the currentI3 d can be further influenced (e.g., shaped, distorted, etc.) by one ormore components of the receiver 204 a. For example, circuits 210 and 212can include inductive and/or capacitive components that can alter thephase or shape of the current I3 d. In some cases, the distortions ofthe current I3 d can create challenges in operating the rectifierswitches, as described further below.

The exemplary receiver 204 a can include filter circuit 212 (including,e.g., one or more inductive components L3 dA, L3 dB, one or morecapacitive components, etc.) coupled to the receiving resonator and/ormatching circuit 210. The filter circuit 212 can be configured to changecharacteristics (e.g., reduce distortions) of the current I3 d.

The filter circuit 212 can be coupled to the rectifier 214 a (e.g., ahalf-bridge inverter, a full-bridge inverter, etc.), which can includetwo or more switches (e.g., transistors Q5, Q6, Q7, and Q8). Theexemplary rectifier 214 a can be coupled directly or indirectly to aload 216 (e.g., a battery). In some embodiments, a current sensor 218can determine (e.g., measure, sense, etc.) the characteristics of thecurrent I3 d. The current sensor 218 can be coupled at the output of thefilter 212 and/or input of the rectifier 214. For example, the currentsensor 218 may determine the phase of the current I3 d at the input ofthe rectifier 214. The sensor signal may be provided to a processorand/or controller (e.g., controller 126) for processing. In someembodiments, the processor and/or controller may generate controlsignals (e.g., PWM signals) for controlling one or more switches of therectifier 214 based on the current sensor 218 signal(s). The processorand/or controller can provide the control signals (e.g., PWM5, PWM6,PWM7, PWM8) to one or more switches (e.g., Q5, Q6, Q7, Q8, respectively)of the rectifier 214. In some embodiments, the current sensor 218 caninclude a zero-crossing detector configured to detect zero-crossings bythe current I3 d, as described in further detail below. The detectorsignal may be provided to the controller to determining the controlsignals for the switches.

In some embodiments, the control signals may cause the rectifierswitches to operate in various modes. The modes can include hardswitching and/or soft switching (e.g., zero voltage switching). In someembodiments, the rectifier switches can operate in one mode during afirst time period and operate in another mode during a second timeperiod. In some cases, the switches may alternate or transition betweentwo modes during a given time period.

The following non-limiting exemplary wireless power system 200specifications are referenced herein:

-   -   The transmitter coil L1 s can be disposed on a single or        multiple layers of ferrite.    -   The system 200 is configured to deliver approximately 11.3 kW of        power to the load 216.    -   The receiver coil L1 d can have 15 or less turns, 20 or less        turns, 25 or less turns, etc. (e.g., approximately 16 turns).    -   The matching can be configured for a voltage range Vbus=300-900        V (e.g., 640-840 V).

FIG. 2B illustrates an alternative embodiment of a wireless powerreceiver 204 b including an active rectifier 214 b. Receiver 204 bincludes the same or similar components described herein for receiver204 a. However, the rectifier 214 b is a full-bridge active rectifierhaving diodes D5, D6 in the high-side positions and switches Q7, Q8 inthe low-side positions.

FIG. 2C illustrates another alternative embodiment of a wireless powerreceiver 204 c including an active rectifier 214 c. Receiver 204 cincludes the same or similar components described herein for receiver204 a. However, the rectifier 214 c is a full-bridge active rectifierhaving (i) diodes D6, D8 coupled between input node 220 and the outputof the rectifier 214 c and (ii) switches Q5, Q7 coupled between inputnode 222 and the output of the rectifier 214 c. In an alternativeembodiment, an active rectifier can be a full-bridge active rectifierhaving switches Q6, Q8 (replacing diodes D6, D8 in FIG. 2C) coupledbetween input node 220 and the output of the rectifier and (ii) diodesD5, D7 (replacing switches Q5, Q7 illustrated in FIG. 2C) coupledbetween input node 222 and the output of the rectifier. Note that one ormore of the following methods can be used to control the switches ofrectifier 214 a, 214 b, or 214 c.

First Exemplary Method—Resistive Input Impedance

FIG. 3A is a schematic of an exemplary wireless power system 300utilizing active rectification. Note that the system 300 can includecomponents of system 200 (e.g., rectifier 214 a, 214 b, or 214 c) asdiscussed above. In some embodiments, system 300 can include a receiver303 having one or more capacitors C3 dA coupled between inductor L3 dAand a first input 301 a of the rectifier 214 a and one or morecapacitors C3 dB coupled between L3 dB and a second input 301 b of therectifier 214 a.

FIG. 3B illustrates an exemplary workflow 302 corresponding to exemplarymethod for determining the control signals (e.g., PWM5, PWM6, PWM7,PWM8) for the rectifier switches (e.g., Q5, Q6, Q7, Q8, respectively)based on the input current I3 d. FIG. 3C is a set of plots illustratingvarious signals in the generation of the control signals as a functionof time. FIG. 3D illustrates an exemplary method 304 for determiningcontrol signals for active rectification in a rectifier presenting aresistive impedance to one or more portions of the wireless power system(e.g., the transmitter 202, components between Vbus and arrow 305,etc.). For the sake of clarity and conciseness, FIGS. 3A-3D arediscussed together herein.

Referring to FIG. 3B, the current I3 d can be inputted to zero-crossingdetector 306 (e.g., of control system 322). An exemplary current I3 d isprovided in FIG. 3C(i). In step 308 of exemplary active rectificationmethod 304, the detector 306 is configured to detect thezero-crossing(s) of the input current I3 d. Referring to FIG. 3C(ii),the detector 306 can output a zero-crossing detection signal Vzcdindicating the zero-crossings of current signal I3 d. For example, thecurrent I3 d has a rising zero-crossing at time t0 and a fallingzero-crossing at time t5. Zero-crossing information can be used tosynchronize switching patterns of Q5, Q6, Q7, and/or Q8 switches to theI3 d current zero-crossings, as illustrated in FIG. 3C(iii) and FIG.3C(v). In particular, the rising edge 310 a (at time t0) and fallingedge 310 b (at time t5) of signal Vzcd can be used to time the switchingsignals PWM_(pdt5) and PWM_(pdt7) (as illustrated in FIG. 3C(iii)) andthe switching signals PWM_(pdt6) and PWM_(pdt8) (as illustrated in FIG.3C(v)).

The signal having the zero-crossing information (e.g., voltage Vzcd) canbe provided to a delay block 312 (e.g., of control system 322). In step314, the delay block 312 can determine a first delay time T_(del1) and asecond delay time T_(del2) based on system parameter(s) (e.g., β, asdescribed further below). The exemplary delay block 312 may beconfigured to provide one or more time delays according to the followingrelationships:T _(del1)=(270−β)/360*T _(period)  Time delay 1:T _(del2)=(90+β)/360*T _(period) −T _(dead)  Time delay 2:where 0≤β≤90°, T_(period) is a single period in time of the input signalI3 d, and time T_(dead) is a fixed quantity (e.g., on the order ofhundreds of nanoseconds) based on the specifications of the transistorsand/or gate drivers used. Time T_(dead) can be sufficiently large sothat no shoot-through condition occurs during phase lags and so that onetransistor of a pair of transistors is conducting at a given time. Forexample, switch Q5 should not be on at the same time as its pair, switchQ7. As described below, these time delays can be used to generatedelayed control signals (e.g., PWM_(pdt5), PWM_(pdt6), PWM_(pdt7),PWM_(pdt8)). The delayed control signals can be provided to a dead-timecompensation block 306.

Parameter β can be determined by a controller depending on a preferredsystem optimization. In some embodiments, the controller may beconfigured to create an equivalent impedance of the rectifier 214 andtherefore select β to achieve that impedance. In some embodiments, thecontroller may be configured to maintain the impedance of the rectifierdespite the changes in battery voltage (at load 216) and thereforeselect β to achieve maintenance. In some embodiments, the controller maybe configured to maintain the power provided to the load 216 within aparticular range and therefore select β to achieve maintenance of power.In some embodiments, β may be selected to maintain desirable coilcurrent (e.g., in L1 d) on the receiver side.

In some embodiments, T_(del1) can be from 0.5 of a period (T_(period))to 0.75 of a period (T_(period)). In some embodiments, T_(del2) can befrom 0.25 of a period (T_(period)) to 0.5 of a period (T_(period)).Delay time T_(del1) can be used for the control signals for switches Q5and Q7. Delay time T_(del2) can be used for the control switches forswitches Q6 and Q8. Note that switches Q5 and Q7 form soft-switchingphase-leg, while switches Q6 and Q8 form hard-switching phase-leg. Inthe example illustrated in FIG. 3C, delay time T_(del1) is equivalent tothe difference between time t0 and t6 and delay time T_(del2) isequivalent to the difference between t0 and t3.

In step 316, control system 322 (e.g., controller 318 and/or processor320 coupled to the switches) can generate the first and second “pre-deadtime” control signals PWM_(pdt5), PWM_(pdt7) for the first and secondrectifier switches Q5, Q7, respectively, based on the first delay timeT_(del1). For example, the rising and falling edges 310 a, 310 b ofsignal Vzcd are used to produce the respective edges 324 a, 324 b ofsignals PWM_(pdt5) and PWM_(pdt7).

In step 326, control system 322 can generate the third and fourth“pre-dead time” control signals PWM_(pdt6), PWM_(pdt8) for the third andfourth rectifier switches Q6, Q8, respectively, based on the seconddelay time T_(del2). For example, the rising and falling edges 310 a,310 b of signal Vzcd are used to produce the respective edges 328 a, 328b of signals PWM_(pdt6) and PWM_(pdt8).

In step 328, the dead-time insertion block 330 can insert a dead timeT_(dead) between the first pre-dead time control signal and the secondpre-dead time control signal, PWM_(pdt5) and PWM_(pdt7), respectively.By inserting dead time between signals PWM_(pdt5) and PWM_(pdt7), thecontrol system 322 produces control signals PWM5, PWM7 for respectiverectifier switches Q5, Q7. In FIG. 3C(iv), arrows 332 a and 332 bindicate the dead-time T_(dead) between the respective edges of signalsPWM5, PWM7 (e.g., such that T_(dead)=t7−t6 and T_(dead)=t12−t11).

In step 334, the dead-time insertion block 330 can insert a dead timeT_(dead) between the third pre-dead time control signal and the fourthpre-dead time control signal, PWM_(pdt6) and PWM_(pdt8), respectively.By inserting dead time between signals PWM_(pdt6) and PWM_(pdt8), thecontrol system 322 produces control signals PWM6, PWM8 for respectiverectifier switches Q6, Q8. In FIG. 3C(vi), arrows 336 a and 336 bindicate the dead-time T_(dead) between the edges of signals PWM6, PWM8(e.g., such that T_(dead)=t4−t3 and T_(dead)=t9−t8).

In step 338, the control system 322 can provide control signals to therespective rectifier switches. In the example of a full-bridge rectifierhaving four switches (e.g., as in rectifier 214 a), control signal PWM5is generated for switch Q5; control signal PWM6 is generated for switchQ6; control signal PWM7 is generated for switch Q7; and control signalPWM8 is generated for switch Q8. In another example, for a rectifierhaving two high-side diodes and two low-side switches Q7 and Q8 (e.g.,as in rectifier 214 b), control signals PWM7 and PWM8 are provided torespective switch Q7 and Q8 only. In yet another example, for rectifier214 c, control signals PWM5 and PWM7 are provided to respective switchQ5 and Q8.

For an exemplary receiver 303 of the system 300 having theabove-provided specifications and utilizing workflow 302, the value offilter inductor L3 dA in system 300 can be approximately 35 μH. Seriescompensating capacitor can be used to maintain the same impedance at 85kHz as the 7 uH inductor.

Second Exemplary Method—Resistive Input Impedance

FIG. 4A illustrates a workflow 400 of an exemplary method for generatingcontrol signals for the rectifier switches based on input current I3 d.FIG. 4B is a set of plots illustrating various signals in the generationof the control signals as a function of time. FIG. 4C illustrates anexemplary method 402 for generating the control signals for a rectifierpresenting a resistive impedance to one or more portions of the wirelesspower system (e.g., the transmitter 202, components between Vbus andarrow 305, etc.). For the sake of clarity and conciseness, FIGS. 4A-4Care discussed together herein.

Referring to FIG. 4A, the current I3 d can be provided to zero-crossingdetector 406 (e.g., of processor 320). An exemplary current I3 d isprovided in FIG. 4B(i). In step 404 of exemplary method 402, thezero-crossing detector 406 can detect the rising zero-crossing at timeto of the rising input current signal I3 d and the falling zero-crossingat time t₅ of the falling input current signal I3 d. The zero-crossingdetector 406 can output a voltage signal Vzcd having zero-crossinginformation of the current signal I3 d.

In step 408, a phase delay lock (PLL) block 410 can generate a PLLsignal based on the rising zero-crossing and the falling zero-crossingof current I3 d. Block 410 outputs PLL signal “SYNC”, as illustrated inFIG. 4B(iii), which is a signal “synchronized” to the zero-crossingsignal Vzcd such that signal SYNC is in phase with signal Vzcd. In someembodiments, the SYNC signal may be a copy of the voltage signal Vzcd.In some embodiments, the SYNC signal may have the same phase and/orfrequency of the signal Vzcd with a magnitude different from voltagesignal Vzcd. For example, the rising edge of Vzcd corresponds to therising edge of SYNC at time t0 (indicated by arrow 412 a) and thefalling edge of Vzcd corresponds to the falling edge of SYNC at time t5(indicated by arrow 412 b).

In step 413, the delay block 414 can determine a first delay timeT_(del1) and a second delay time T_(del2) based on system parameter(s)(e.g., β as described further below). The delay block 414 can produceone or more time delays according to the following relationships:T _(del1)=(270−β)/360*T _(period)  Time delay 1:T _(del2)=(90+β)/360*T _(period) −T _(dead)  Time delay 2:where 0≤β≤90°, T_(period) is a single period in time of the input signalI3 d, and time T_(dead) is a fixed quantity based on the specificationsof the transistors and/or gate drivers. T_(dead) can be sufficientlylarge so that no shoot-through condition occurs during phase lags and sothat one transistor of a pair of transistors is conducting at a giventime. For example, switch Q5 is not on at the same time as its pair,switch Q7. The delayed signal can be provided to a dead-timecompensation block 428.

Parameter β can be determined by a controller depending on a preferredsystem optimization. In some embodiments, the controller may beconfigured to create an equivalent impedance of the rectifier 214 andtherefore select β to achieve that impedance. In some embodiments, thecontroller may be configured to maintain the impedance of the rectifierdespite the changes in battery voltage (at load 216) and thereforeselect β to achieve maintenance. In some embodiments, the controller maybe configured to maintain the power provided to the load 216 within aparticular range and therefore select β to achieve maintenance of power.For the example provided in FIG. 4B, parameter β is selected to be 47degrees.

In some embodiments, T_(del1) can be from 0.5 of a period (T_(period))to 0.75 of a period (T_(period)). In some embodiments, T_(del2) can befrom 0.25 of a period (T_(period)) to 0.5 of a period (T_(period)).Delay time T_(del1) can be used for the control signals for switches Q5and Q7. Delay time T_(del2) can be used for the control switches forswitches Q6 and Q8. Note that switches Q5 and Q7 form the soft-switchingphase leg, while switches Q6 and Q8 form the hard-switching phase leg.In the example illustrated in FIG. 4B, delay time T_(del1) is equivalentto the difference between time t0 and t6 and delay time T_(del2) isequivalent to the difference between t0 and t3.

In step 416, delay block 414 can generate the “pre-dead time” first andsecond control signals PWM_(pdt5) and PWM_(pdt7), respectively for thefirst and second rectifier switches, Q5 and Q7, respectively, based onthe PLL signal SYNC and the first delay time T_(del1). For example, therising and falling edges 420 a, 420 b of signal SYNC are used to producethe edges 420 a, 420 b of signals PWM_(pdt5) and PWM_(pdt7).

In step 422, delay block 414 can generate the “pre-dead time” third andfourth control signals PWM_(pdt6) and PWM_(pdt8), respectively for thethird and fourth rectifier switches Q6 and Q8, respectively, based onthe PLL signal SYNC and the second delay time T_(del2). For example, therising and falling edges 412 a, 412 b of signal SYNC are used to producethe edges 424 a, 424 b of signals PWM_(pdt6) and PWM_(pdt8).

In step 426, dead-time compensation block 428 can insert a dead timeT_(dead) between the “pre-dead time” first control signal and the“pre-dead time” second control signal PWM_(pdt5) and PWM_(pdt7),respectively. Dead-time insertion is illustrated in FIG. 4B(v). Byinserting dead time between time t6 and time t7, the control system 322produces control signals PWM5, PWM7 for respective rectifier switchesQ5, Q7. In FIG. 4B(v), arrows 430 a, 430 b indicate the dead timeT_(dead) between the respective edges of signals PWM5, PWM7 (e.g., suchthat T_(dead)=t7−t6 and T_(dead)=t11−t12).

In step 432, block 428 can insert a dead time T_(dead) between the“pre-dead time” third control signal and the “pre-dead time” fourthcontrol signal PWM_(pdt6) and PWM_(pdt8), respectively. Dead-timeinsertion is illustrated in FIG. 4B(vii). By inserting dead time betweentime t3 and t4, the control system produces control signals PWM6, PWM8for respective rectifier switches Q6, Q8. In FIG. 4B(vii), arrows 434 a,434 b indicate the dead time T_(dead) between the respective edges ofsignals PWM6, PWM8 (e.g., such that T_(dead)=t4−t3 and T_(dead)=t9−t8).

In step 434, control system 322 can provide control signals (e.g., PWM5,PWM6, PWM7, and PWM8) to the respective rectifier switches (e.g., Q5,Q6, Q7, and Q8, respectively). In the example of a full-bridge rectifierhaving four switches (e.g., as in rectifier 214 a), control signal PWM5is generated for switch Q5; control signal PWM6 is generated for switchQ6; control signal PWM7 is generated for switch Q7; and control signalPWM8 is generated for switch Q8. In another example, for a rectifierhaving two high-side diodes and two low-side switches Q7 and Q8 (e.g.,as in rectifier 214 b), control signals PWM7 and PWM8 are provided torespective switch Q7 and Q8 only. In yet another example, for rectifier214 c, control signals PWM5 and PWM7 are provided to respective switchQ5 and Q8.

For an exemplary receiver 204 of the system 200 having theabove-provided specifications, the value of filter inductors L3 sA, L3sB in method 402 can be approximately 14 μH. Note that the filterinductors L3 sA, L3 sB of method 402 is approximately five times less invalue as the filter inductors L3 sA, L3 sB of method 304. This canresult in a reduced footprint (e.g., size, volume, etc.) and/or cost fora system employing method 402.

Third Exemplary Method—Capacitive Input Impedance

FIG. 5A illustrates a workflow 500 corresponding to an exemplary methodfor generating the control signals for the rectifier switches based oninput current I3 d. FIG. 5B is a set of plots illustrating varioussignals in the generation of the control signals as a function of time.FIG. 5C illustrates an exemplary active rectification method 502 in arectifier presenting a capacitive impedance to one or more portions ofthe wireless power system (e.g., the transmitter 202, components betweenVbus and arrow 305, etc.). For the sake of clarity and conciseness,FIGS. 5A-5C are discussed together herein.

In step 504, a sensor 506 can receive the input current I3 d. In someembodiments, sensor 506 can include a filter (e.g., a bandpass filter, alow-pass filter, a high-pass filter, etc.). In a preferred embodiment,the exemplary sensor 506 includes a bandpass filter characterized by thefollowing transfer function:

${H(s)} = \frac{\frac{\omega_{0}}{Q_{f}} \cdot s}{s^{2} + {\frac{\omega_{0}}{Q_{f}} \cdot s} + \omega_{0}^{2}}$where ω₀=2*π/T_(period) and Qf is the quality factor of the filter. Thefiltering of the current I3 d may stabilize the modulator and therebyenable stable output control (PWM) signals. The filtered current signalI3 dmf is then provided to a zero-crossing detector 508.

In step 510, the zero-crossing detector 508 can detect the risingzero-crossing of the filtered current signal I3 dmf and the fallingzero-crossing of the filtered current signal I3 dmf. The detector 508can produce an output signal ZCD (e.g., a voltage Vzcd and/or currentIzcd) having zero-crossing information. For example, as illustrated inFIG. 5B(iii), edge 512 a of signal ZCD corresponds to the risingzero-crossing of signal I3 dmf (at time t0) and edge 512 b of signal ZCDcorresponds to falling zero-crossing of signal I3 dmf (at time t4).

In step 514, delay block 516 can determine a delay time T_(del1) basedon system parameter(s) (e.g., β as described further below). The delayblock 516 can produce one or more time delays according to the followingrelationship:T _(del1)(270−β)/360*T _(period)  Time delay:where 0≤β≤90°, T_(period) is a single period in time of the input signalZCD, and time T_(dead) is a fixed quantity based on the specificationsof the transistors and/or gate drivers. T_(dead) can be sufficientlylarge so that no shoot-through condition occurs during phase lags and sothat one transistor of a pair of transistors is conducting at a giventime. For example, switch Q5 is not on at the same time as its pair,switch Q7. The delayed signals PWM_(pdt5), PWM_(pdt7) can be provided toa dead-time compensation block 518.

Parameter β can be determined by a controller depending on a preferredsystem optimization. In some embodiments, the controller may beconfigured to create an equivalent impedance of the rectifier 214 andtherefore select β to achieve that impedance. In some embodiments, thecontroller may be configured to maintain the impedance of the rectifierconstant despite the changes in battery voltage (at load 216) andtherefore select β to achieve maintenance. In some embodiments, thecontroller may be configured to maintain the power provided to the load216 within a particular range and therefore select β to achievemaintenance of power. In the example provided in FIG. 5B, parameter βwas selected to be 75 degrees.

In step 520, the delay block 516 can generate the “pre-dead time” firstand second control signals PWM_(pdt5) and PWM_(pdt7), respectively, forthe first and second rectifier switches Q5 and

Q7, respectively, based on the delay time T_(del1). In the exampleillustrated in FIG. 5B, delay time T_(del1) is equivalent to thedifference between time t0 and t5. For example, the rising and fallingedges 512 a, 512 b of signal ZCD are used to produce the edges 522 a,522 b of signals PWM_(pdt5) and PWM_(pdt7).

In step 524, dead-time insertion block 526 can include inserting a deadtime T_(dead) between the “pre-dead time” first control signal and the“pre-dead time” second control signal. By inserting dead time betweentime t5 and t6, the control system 322 produces control signalsPWM_(pdt5) and PWM_(pdt7) for respective rectifier switches Q5, Q7. Inparticular, arrows 528 a, 528 b indicate the dead time T_(dead) betweenthe edges of signals PWM5, PWM7 in plot FIG. 5B(v). Note thatcommutation of the diode half-bridge (e.g., diodes D6, D8) occursbetween times t3 and t7 such that t7−t3=T_(period)/2.

In step 530, control system 322 can provide control signals PWM5, PWM7to the respective rectifier switches Q5, Q7 (e.g., of rectifier 214 c).

One advantage is that the exemplary method 502 can enable the use of asmaller inductor at filter inductors L3 sA, L3 sB, thereby reducing thephysical volume of the receiver 204. The exemplary method 502 may alsoachieve greater efficiency as compared to methods which include theactive control of four switches (e.g., Q5, Q6, Q7, and Q8) of therectifier 214.

Fourth Exemplary Method—Phase Shift Control

FIG. 6A illustrates a workflow 600 for an exemplary method forgenerating control signals for rectifier switches by controlling therelative phase shift between input current I3 d and input voltage VAC(also referred to as Vacd). FIGS. 6B-6C are a set of plots illustratingthe generation of control signals as a function of time according toworkflow 600. FIG. 6D illustrates a method 602 for generating controlsignals according to the workflow 600. Note that the control scheme ofmethod 602 may be implemented in the mixed signal or digital domain. Forthe sake of clarity and conciseness, FIGS. 6A-6D are discussed togetherherein.

Referring to FIG. 6A, current I3 d can be inputted to a zero-crossingdetector 604 (e.g., of control system 322). An exemplary current I3 d isprovided in FIG. 6B(v). In step 606, detector 604 is configured todetect the zero-crossing(s) of input current I3 d. Referring to FIG.6B(i), the detector 604 can output a zero-crossing detection signal Vzcdindicating the zero-crossings of the current signal I3 d. As describedherein for other methods, zero-crossing information can be used tosynchronize the switching patterns of switches Q5, Q6, Q7, and/or Q8 tothe current zero-crossings.

In step 608, a phase delay lock (PLL) block 610 can generate a PLLsignal based on the rising zero-crossing and the falling zero-crossingof current I3 d. Block 610 outputs PLL signal “SYNC”, as illustrated inFIG. 6B(ii), which is a signal “synchronized” to the zero-crossingsignal Vzcd such that signal SYNC is in phase with signal Vzcd. In someembodiments, the SYNC signal may have a frequency at least two times thefrequency of the voltage signal Vzcd. In some embodiments, the SYNCsignal may have a magnitude different from voltage signal Vzcd. Forexample, the rising edge of Vzcd corresponds to a falling edge of SYNC(indicated by arrow 612 a) and the falling edge of Vzcd corresponds tothe rising edge of SYNC (indicated by arrow 612 b) such that one periodof signal Vzcd corresponds to two periods of signal SYNC.

In step 614, the ramp generation block 616 (e.g., of control system 322)can generate at least one ramp signal Vramp based on the output PLLsignal. Ramp signal Vramp is used to produce PWM signals with the helpof Vdc1 and Vdc2 defined with the following relationships:

$V_{dc1} \approx {1 - \frac{\beta - \varphi}{180}}$$V_{dc2} \approx \frac{\beta + \varphi}{180}$where parameter β is selected to control the resistive impedance of therectifier and is selected according to desired system optimization (asdescribed above) and parameter φ is selected to control the capacitiveimpedance of the rectifier. In the example provided in FIGS. 6B-6C,parameter β=70 and parameter φ=20 for an exemplary system 200 configuredto deliver 8.3 kW to the battery 216.

In step 618, the PWM generator 620 (e.g., of control 622) can generatepre-dead time PWM signals PWM_(pdt5), PWM_(pdt6), PWM_(pdt7), PWM_(pdt8)for switches Q5, Q6, Q7, Q8 based on the signals Vdc1 and Vdc2. In someembodiments, the control system (e.g., the modulator of system 322) canmodulate signals Vdc1 and Vdc2 to form control signals (e.g., pre-deadtime PWM signals).

In frequency divider block 622, the frequency of the pre-dead time PWMsignals is divided. In some embodiments, the frequency is divided by afactor of 2. In some embodiments, the frequency is divided by a factorgreater than 2 (e.g., 2.5, 3, 4, etc.).

In step 624, dead-time compensation block 626 can insert a dead timeT_(dead) between the pre-dead time first control signal PWM_(pdt5) andthe pre-dead time second control signal PWM_(pdt7). By inserting deadtime, the control system 322 produces control signals PWM5, PWM7 forrespective rectifier switches Q5, Q7.

In step 628, block 626 can insert a dead time T_(dead) between thepre-dead time third control signal PWM_(pdt6) and the “pre-dead time”fourth control signal PWM_(pdt8). By inserting dead time, the controlsystem produces control signals PWM6, PWM8 for respective rectifierswitches Q6, Q8.

In step 630, control system 322 can provide control signals (e.g., PWM5,PWM6, PWM7, and PWM8) to the respective rectifier switches (e.g., Q5,Q6, Q7, and Q8, respectively). In the example of a full-bridge rectifierhaving four switches (e.g., as in rectifier 214 a), control signal PWM5is generated for switch Q5; control signal PWM6 is generated for switchQ6; control signal PWM7 is generated for switch Q7; and control signalPWM8 is generated for switch Q8. In another example, for a rectifierhaving two high-side diodes and two low-side switches Q7 and Q8 (e.g.,as in rectifier 214 b), control signals PWM7 and PWM8 are provided torespective switch Q7 and Q8 only. In yet another example, for rectifier214 c, control signals PWM5 and PWM7 are provided to respective switchQ5 and Q8.

Application to Bidirectional Wireless Power Transmission

In various embodiments, the active rectification systems and methodsdescribed herein can be employed in bidirectional wireless powersystems. For instance, a wireless power system may be configured suchthat wireless power is transmitted from a transmitter to a receiver(also referred to as “unidirectional”). In some cases, a wireless powersystem may be configured such that wireless power is transmitted from afirst device to a second device (e.g., from a transmitter to a receiver)and/or from a second device to the first device (e.g., from a receiverto transmitter). Examples of bidirectional wireless power systems andmethods can be found in U.S. Publication No. 2019/0006836 titled“Protection and control of wireless power systems” and published Jan. 3,2019, and U.S. Publication No. 2020/0094696 titled “Wireless powertransmission in electric vehicles” and published Mar. 26, 2020.

FIG. 7 shows a schematic of an exemplary bidirectional wireless powersystem 700. The schematic depicts both a transmitter (Tx) side wirelesspower device 700 a and a receiver (Rx) side wireless power device 700 b.As noted above, the Tx-side wireless power device 700 a generallyoperates as a wireless power transmitter for the case of a similarunidirectional wireless power system (e.g., system 200 or 300). TheTx-side device 700 a may also be referred to as a ground assembly (GA)or GA-side device when used in the context of a wireless power devicecoupled to an electric vehicle or other mobile vehicle. As discussedbelow, however, in the bidirectional system the Tx-side refers generallyto a wireless power device that is coupled to or configured to becoupled to a stationary power supply or load such as a power grid, ACgenerator, etc. Furthermore, the Tx-side system is generally capable ofhandling higher power, voltage, or current transients than the Rx-sidewireless power device 700 b. On the other hand, the Rx-side wirelesspower device 700 b generally operates as a wireless power receiver forthe case of a similar unidirectional wireless power transfer system(e.g., system 200 or 300). As discussed below, however, in thebidirectional system the Rx-side refers generally to a wireless powerdevice that is coupled to or configured to be coupled to a mobile (orgenerally more limited) power supply or load such as a battery or abattery powered device (e.g., a computing device or an electricvehicle). The Rx-side wireless power device 700 b can also be referredto as a vehicle assembly (VA) or VA-side device when used in the contextof a wireless power device coupled to an electric vehicle or othermobile vehicle.

In exemplary bidirectional system 700, both the Tx-side device 700 a andthe Rx-side device 700 b include an inverter-rectifier 702. Theinverter-rectifier 702 can include a bridge configuration of switchingelements and/or diodes. For example, the inverter-rectifier 702 caninclude active switching elements, such as MOSFETs, which permit theinverter-rectifier 702 to operate as either an inverter or a rectifierin a bidirectional system. As discussed in more detail below, theoperating mode (also referred to herein as an “operating personality”)of the inverter-rectifier 702 can be controlled based on the pattern ofPWM control signals supplied to the switching elements. In someembodiments, the inverter-rectifier 702 may be operated according to oneor more active rectification methods (e.g., method 304, 402, 502, and/or602) described herein.

The system 700 is able to power a load with power transmission in afirst direction (e.g., a normal power flow direction from transmitter700 a to receiver 700 b), such as a battery of a vehicle, off of powerinput to the transmitter 700 a. Alternatively, the system 700 can supplypower in a second direction (e.g., a reverse power flow direction), suchas suppling power to a power grid coupled to the Tx-side device 700 afrom a battery of an electric vehicle coupled to the Rx-side device 700b. As another example, the bidirectional system 700 can be used to powera home during a power outage from a battery of an electric vehiclebattery parked in a garage.

Where single components are shown, including resistors, inductors, andcapacitors, banks of components, including in series and/or parallel canbe utilized. Where tunable components are shown, fixed components can beincluded in series and/or parallel with the tunable components. In someimplementations, the controller 122 a and 122 b can be combined in asingle controller 720. Likewise, in some implementations, the controller126 a and 126 b can be combined in a single controller 740.

In some implementations, the controllers 720 and 740 include abidirectional manager. The bidirectional manager coordinates theconfiguration of different hardware and software components wirelesspower device (e.g., either 700 a or 700 b) according to the direction ofpower flow as indicated by an operating personality assigned to thedevice. For example, an operating personality of INV indicates that theinverter-rectifier is operating as an inverter and therefore thewireless power device 700 a/700 b is operating as a transmitter.Similarly, for example, an operating personality of REC indicates thatthe inverter-rectifier is operating as a rectifier and therefore thewireless power device 700 a/700 b is operating as a receiver. Thebidirectional manager also coordinates transitions from one direction ofpower flow to the opposite direction of power flow. For example, thebidirectional manager of the Rx-side device 700 b can communicate withthe bidirectional manager of the Rx-side device 700 a through a wirelesscommunication link 750 (e.g., a Wi-Fi link) to coordinate a powerreversal. The bidirectional manger can be implemented as separatecontroller within each device 700 a/700 b or in software.

More specifically, various hardware and software components of thesystem can have different operating setpoints, modes and/or ranges ofoperations depending on the direction of flow of power, and byextension, the operating personality of the wireless power device 700a/700 b. The various operating set points, modes and/or ranges ofoperation can be stored in memory or in hardware. Each component of thesystem (e.g. the inverter-rectifier 702, tunable matching network (TMN)703, and other components) including various controllers, filters,communication systems, and/or protection systems can assume a different“operating personality” depending on the direction of power flow.

The wireless power device's bidirectional manager can assign anappropriate personality at system startup and/or during a power flowtransition based on the expected direction of power flow through thewireless power system 700 as a whole. For example, upon receipt of acommand to switch from one mode of operation for the system to another(for example, by an operator interface, and/or user interface connectedto either or all of the controllers, on either or both sides of thesystem or off system, such as on a network, the grid, or a mobiledevice), the bidirectional manager can assign the various componentcontrollers (e.g., 122 a, 122 b, 126 a, and 126 b) a respectiveoperating personality. Each controller can use the assigned operatingpersonality to identify and load appropriate operating processes orsoftware code to control associated components of the wireless powertransfer device 700 a/700 b. For instance, when an inverter-rectifiercontroller is assigned an operating personality of an inverter (e.g.,INV), the controller will load software code to generate PWM controlsignal patterns to operate the inverter-rectifier switching elements togenerate AC output signals from a DC input signal. On the other hand,when an inverter-rectifier controller is assigned an operatingpersonality of a rectifier (e.g., REC), the controller will loadsoftware code to generate PWM control signal patterns to operate theinverter-rectifier switching elements to rectify an AC input signal intoa DC output signal.

Furthermore, the bidirectional manager can provide the power demand, thepower flow direction, choose the appropriate software code blocks, andassign personalities to sub-controllers or other controller(s). Thebidirectional manager can determine the errors that are recoverable ornot recoverable, depending on the side the system the controller islocated on, and the operating personality it assumes for components ofthe system. The operational personalities can be assigned based on theexpected power flow direction, e.g. vehicle-to-grid (V2G) power flow, orgrid-to-vehicle (G2V) power flow. Moreover, the bidirectional managercan determine the time and/or mode for recovery for those errors and/orclear errors when they are recovered so no user intervention is needed.The bidirectional manager can communicate with the user, thecontroller(s) of the other side of the system (e.g., the bidirectionalmanager on the other side of the system).

The bidirectional manager can receive notification of an error from acomponent of the wireless power system and the error messages can beallocated to other components of the wireless power system, eitherdirectly by the bidirectional manager or after a callback request fromthe components.

The bidirectional manager can receive communication from components ofthe wireless power system (e.g., via Wi-Fi from components from theother side of the system). The bidirectional manager can fulfillcallback requests from components for messages related to the component,or can allocate the message to the relevant components. Thebidirectional manager can control, including dynamically, the privilegesof the components of the wireless power system to receive and send errorand communication messages. The bidirectional manager can be responsiblefor controlling the components of the wireless power system during thetransition phases, including handling any error conduction arising fromthe change of power transfer direction (both V2G and G2V transitions).For example, the bidirectional manager can oversee turning down ofpower, confirm power has fully or partially turned off, and sequence thecomponents of the system to turn on (while assigning personalities tothe components).

As an example, the bidirectional manager on the transmitter controllerreceives a command to turn on power from idle, the bidirectional managermay assign G2V personality to the various controllers and hardware inthe system. Upon receipt of a communication to change the powertransmission direction, the bidirectional manager communicates betweenthe transmitter and receiver to change power transmission direction. Thebidirectional manager can be responsible for handling any error arisingfrom the change of power transmission direction, including during thepower down of the first direction and the power up of the seconddirection. When the error is cleared, the bidirectional manager canassign personality to the controller(s), for example, by selecting asubset of instructions from a non-transitory computer readable medium,or causing the controller(s) to select the subset of instructions.

In some implementations, each controller of the system (e.g., adedicated inverter-rectifier processor, or a dedicated TMN processor, ora dedicated transmitter or receiver processor) can contain abidirectional manager. The bidirectional manager can operate as atop-level manager.

Generally, assigning a personality to components/controllers can allowfor modularity, non-redundant parts, code, and memory, allows for fasterand on-the-fly switchover from G2V (grid-to-vehicle power flow) to V2G(vehicle-to-grid power flow) and back.

FIG. 8 depicts flowchart of an exemplary bidirectional control process800 that can be executed in accordance with implementations of thepresent disclosure. The example process 800 can be implemented, forexample, by the example wireless power systems disclosed herein. Forexample, the process 800 can be executed between a bidirectional managerof a transmitter wireless power device 700 a and a bidirectional managerof a receiver wireless power device 700 b. Process 800 shows dividedprimary side operations 802 and secondary side 804 operations.Generally, the primary side operations 802 are performed by a receiverwireless power device 700 b while the secondary side operations 704 areperformed by a Tx-side wireless power device 700 a. For example, thereceiver (or device-side) wireless power device 700 b may generally becoupled to a smaller capacity or more limited power source or load.Implementing the receiver wireless power device 700 b as a primarydevice may provide more precise control of the bidirectional controlprocess 800 to prevent exceeding possible lower operating limits of theRx-side system or its load/source. In some examples, the example process800 can be provided by one or more computer-executable programs executedusing one or more computing devices, processors, or microcontrollers.For example, the example process 800, or portions thereof, can beprovided by one or more programs executed by control circuitry ofwireless power devices 700 a, 700 b.

The primary device initiates a power flow transition within the wirelesspower system. The initiation may be prompted by a user input, or in someimplementations by an automatic power transition determination performedby the primary device (806). For example, the primary device candetermine to shift power flow based on various criteria including, butnot limited to, state of charge of a battery, time of day, andavailability and/or demand of grid-power. For example, a Rx-sidewireless power device 700 b can be configured to initiate a power flowreversal process when a connected battery is above a threshold chargelevel and a loss of grid power occurs. As another example, a Rx-sidewireless power device 700 b can be configured to initiate a power flowreversal process when a connected battery is above a threshold chargelevel and during a preset time of day. For instance, the Rx-sidewireless power device 700 b can be configured reverse power flow inorder to provide supplemental power to a home during peak load periodsof a power grid (e.g., periods of high demand and/or high energy pricessuch as evenings). In some implementations, the secondary device candetermine when to initiate a power flow transition, but would perform anadditional step of requesting initiation of the power flow transitionfrom the primary device.

The primary device sends instructions to the secondary device to reversethe direction of power flow (808). In response to the instructions, thesecondary device reconfigures for operating in the opposite power flowdirection from its current operations (810). For example, if thesecondary device was operating as a transmitter it will reconfigure foroperation as a receiver. If the secondary device was operating as areceiver it will reconfigure for operation as a transmitter. Forexample, the secondary device's bidirectional manager can coordinatecontroller operations within the secondary device to shut down powerflow in the present direction by, for example, securing operation of theinverter-rectifier, shifting switches to disconnect a load/power supply(as appropriate), toggling bypass switches to dissipate residualcurrents within the secondary device, or a combination thereof.

The secondary device assigns a new operating personality in accordancewith the new power flow direction (812). For example, the secondarydevice's bidirectional manager assigns a new operating personality torespective controllers within the secondary device as appropriate to thenew direction of power flow. The bidirectional power manager can assignthe new operating personality by toggling a flag bit (e.g., TMN_SIDEdiscussed in more detail below) to indicate operation as atransmitter/inverter or operation as a receiver/rectifier.

In response to the new operating personality assignment, the varioussecondary device controllers can reconfigure their respectiveoperations. For example, the controllers can load control algorithms(e.g., software code blocks) to perform operations according to the newpower flow direction. For example, a TMN controller can reset a TMN andload control code for generating appropriate TMN control signals foroperation in according to the new power flow direction. The TMN may needto adjust set points (e.g., impedance values, impedance adjustment stepsizes, and/or protection schemes) to accommodate power transfer in thenew direction or to prepare for power ramp up in the new direction orboth. For example, power flow in a V2G mode may generally be lower thanin a G2V mode, e.g., due to asymmetries between GA and VA side resonatorcoils and/or discharge constraints on a battery. Consequently, TMNand/or inverter-rectifier set points may be different for operating in aV2G mode vice a G2V mode.

The secondary device (e.g., the secondary device's inverter controller)can control the inverter-rectifier operation according to the newoperating personality (814). For example, an inverter-rectifiercontroller can load appropriate algorithms for generating PWM controlsignals for operating as an inverter when the secondary device is atransmitter and operating as a rectifier when the secondary device is areceiver. The specific inverter and rectifier operations are describedin more detail below in reference to FIGS. 9 and 10 .

The secondary device sends a reply to the primary device indicating itsreconfiguration status (816). When the secondary device indicates thatits reconfiguration is still in progress or is stalled, the primarydevice waits and/or resends an instruction 808. By the primary devicewaiting for confirmation that the secondary device has completedupdating its operating personality the process 800 may provide for saferand more robust operations. For example, it may prevent the power flowfrom commencing or reversing with mismatched personalities assigned toeither the secondary or primary device. When the secondary deviceindicates that its reconfiguration is complete, the primary devicereconfigures for operating in the opposite power flow direction from itscurrent operations (818). For example, if the primary device wasoperating as a transmitter it will reconfigure for operation as areceiver. If the primary device was operating as a receiver it willreconfigure for operation as a transmitter. For example, the primarydevice's bidirectional manager can coordinate controller operationswithin the secondary device to shut down power flow in the presentdirection by, for example, securing operation of the inverter-rectifier,shifting switches to disconnect a load/power supply (as appropriate),toggling bypass switches to dissipate residual currents within thesecondary device, or a combination thereof.

The primary device assigns a new operating personality in accordancewith the new power flow direction (820). For example, the primarydevice's bidirectional manager assigns a new operating personality torespective controllers within the primary device as appropriate to thenew direction of power flow. The bidirectional (power) manager canassign the new operating personality by toggling a flag bit (e.g.,TMN_SIDE discussed in more detail below) to indicate operation as atransmitter/inverter or operation as a receiver/rectifier. In responseto the new operating personality assignment, the various primary devicecontrollers can reconfigure their respective operations. For example,the controllers can load control algorithms (e.g., software code blocks)to perform operations according to the new power flow direction. Forexample, a TMN controller can reset a TMN and load control code forgenerating appropriate TMN control signals for operation in according tothe new power flow direction. The TMN may need to adjust set points(e.g., impedance values and/or protection schemes) to accommodate powertransfer in the new direction or to prepare for power ramp up in the newdirection or both.

The primary device (e.g., the primary device's inverter controller) cancontrol the inverter-rectifier operation according to the new operatingpersonality (822). For example, an inverter-rectifier controller canload appropriate algorithms for generating PWM control signals foroperating as an inverter when the secondary device is a transmitter andoperating as a rectifier when the secondary device is a receiver. Insome implementations, a TMN controller in the primary device can controlthe TMN according to the new operating personality. For example, a TMNcontroller on the primary device can load appropriate control algorithmsfor generating TMN adjustment signals for operating as a load coupledTMN in a first direction, or a power supply coupled TMN in a seconddirection.

FIG. 9 depicts a schematic 900 of an exemplary inverter-rectifier 902and a timing diagram 902 illustrating operation of theinverter-rectifier in an inverter operating mode. The schematic 1800shows a phase shifted full-bridge inverter. The inverter bridge circuituses active switching elements Q1, Q2, Q3, and Q4, which can be, forexample, MOSFETs, transistors, FETs, IGBTs, etc.

The timing diagram 902 illustrates the driving signal pattern for theswitches Q1, Q2, Q3, and Q4. The switches are grouped into two legs; LegA (Q1, Q3) and Leg B (Q2, Q4). The corresponding switches in each legare alternately switched on and off by respective PWM control signals.On time and off time, for each gate drive signal G1, G2, G3, and G4 areshown. The dead time td shown is when both gate drivers of the same legare off. The off time may be larger than the on time for each drivingsignal in a period Ts.

The delay time tps between Leg A (Q1 and Q3) and Leg B (Q2 and Q4), whenexpressed in degrees, is known as the phase-shift angle and is a meansfor adjusting the overall power sourced by the inverter-rectifier whenoperating as an inverter. At start-up, output power VAB(t) frominverter-rectifier terminals VA and VB, can have an 11% duty cycle (legphase-shift angle θps=20 degrees). At max power, VAB(t) can be at a 100%duty cycle (leg phase θps=180 degrees). Total power output is controlledby adjusting the delay time tPS between the Leg A and Leg B PWM signals.

In some embodiments, the inverter-rectifier 900 may be operatedaccording to one or more active rectification methods (e.g., method 304,402, 502, and/or 602) described herein. Although a full bridge inverteris shown, in some implementations the inverter-rectifier switches can bearranged in a half-bridge configuration. In some implementations, theinverter-rectifier can implement zero-voltage switching operations toensure the switches are operated when the voltage across them is zero ornear-zero.

FIG. 10 depicts a schematic 1000 of an exemplary inverter-rectifier anda timing diagram 1902 illustrating operation of the inverter-rectifier702 in a rectifier operating mode. FIG. 10 illustrates a synchronousrectifier operation utilizing the same switches as shown in FIG. 9 . Thegate drive signals (G1, G2, G3, G4) corresponding to respective switches(Q1, Q2, Q3, Q4) are shown in the timing diagram 1902. Although zerocurrent switching operation is shown, zero-voltage switching (ZVS)naturally follows the operation and can be used in some implementations.However, ZVS switching in active rectification mode is not shown infigures.

The synchronous rectifier can receive the zero-crossing of the I3 scurrent (shown as I3 d or I3 s in FIG. 7 ) and creates the timing of thesynchronous rectification (zero current switching) as shown in timingdiagram 1002. In the rectifier mode, the inverter-rectifier 702rectifies an AC input signal into a DC output signal by alternatelyswitching on corresponding pairs of switches (Q1/Q4 and Q2/Q3). Forexample, the inverter-rectifier controller (e.g., inverter/protectionand control circuitry) can receive I3 d or I3 s current and/or phasemeasurements from a current or phase sensor (e.g., sensor 218). Theswitches Q1, Q2, Q3, and Q4 can be turned off at the zero current (ornear zero current) of the input to the inverter-rectifier 702, and anappropriate time delay td may be permitted to lapse before operating thenext pair of switches (e.g., Q1 and Q4 or Q2 and Q3). This can preventpower losses within the switch. In some implementations, the time delaymay be adjusted by the system as needed.

In some implementations, during a startup, the inverter-rectifier doesnot begin does not begin switching until the measured input power isabove a threshold value that ensures continuous conduction of the I3 dcurrent. The threshold value can be, e.g., between 2 kW and 4 kW, and/orbetween 20-40% of a target power. During the low power operations belowthe threshold input power value, the input AC signal may be noisy,potentially resulting in inaccurate zero-crossing detections andpossibly large transients for imprecise switching. For example, the I3 dcurrent that is used to generate the PWM synchronization may bediscontinuous and noisy resulting in inaccurate zero-crossing detectionsand possibly large transients or even in a destructive shorting of thepower stage. Instead, rectification can be performed passively whenpower is below the threshold value by conduction through the body-diodesof the switches. In such implementations, the switching operationsperformed above the threshold input power value can be considered anactive rectification mode and the body-diode conduction below thethreshold input power value can be considered a passive rectificationmode.

In some embodiments, the inverter-rectifier 1000 may be operatedaccording to one or more active rectification methods (e.g., method 304,402, 502, and/or 602) described herein.

Hardware and Software Implementations

In some examples, some or all of the processing described above can becarried out on one or more centralized computing devices. In someexamples, some types of processing occur on one device and other typesof processing occur on another device. In some examples, some or all ofthe data described above can be stored in data storage hosted on one ormore centralized computing devices, or via cloud-based storage. In someexamples, some data are stored in one location and other data are storedin another location. In some examples, quantum computing can be used. Insome examples, functional programming languages can be used. In someexamples, electrical memory, such as flash-based memory, can be used.

FIG. 11 is a block diagram of an example computer system 1100 that maybe used in implementing the technology described in this document.General-purpose computers, network appliances, mobile devices, or otherelectronic systems may also include at least portions of the system1100. The system 1100 includes a processor 1110, a memory 1120, astorage device 1130, and an input/output device 1140. Each of thecomponents 1110, 1120, 1130, and 1140 may be interconnected, forexample, using a system bus 1150. The processor 1110 is capable ofprocessing instructions for execution within the system 1100. In someimplementations, the processor 1110 is a single-threaded processor. Insome implementations, the processor 1110 is a multi-threaded processor.The processor 1110 is capable of processing instructions stored in thememory 1120 or on the storage device 1130.

The memory 1120 stores information within the system 1100. In someimplementations, the memory 1120 is a non-transitory computer-readablemedium. In some implementations, the memory 1120 is a volatile memoryunit. In some implementations, the memory 1120 is a non-volatile memoryunit.

The storage device 1130 is capable of providing mass storage for thesystem 1100. In some implementations, the storage device 1130 is anon-transitory computer-readable medium. In various differentimplementations, the storage device 1130 may include, for example, ahard disk device, an optical disk device, a solid-date drive, a flashdrive, or some other large capacity storage device. For example, thestorage device may store long-term data (e.g., database data, filesystem data, etc.). The input/output device 1140 provides input/outputoperations for the system 1100. In some implementations, theinput/output device 1140 may include one or more of a network interfacedevices, e.g., an Ethernet card, a serial communication device, e.g., anRS-232 port, and/or a wireless interface device, e.g., an 802.11 card, a3G wireless modem, or a 4G wireless modem. In some implementations, theinput/output device may include driver devices configured to receiveinput data and send output data to other input/output devices, e.g.,keyboard, printer and display devices 1160. In some examples, mobilecomputing devices, mobile communication devices, and other devices maybe used.

In some implementations, at least a portion of the approaches describedabove may be realized by instructions that upon execution cause one ormore processing devices to carry out the processes and functionsdescribed above. Such instructions may include, for example, interpretedinstructions such as script instructions, or executable code, or otherinstructions stored in a non-transitory computer readable medium. Thestorage device 1130 may be implemented in a distributed way over anetwork, such as a server farm or a set of widely distributed servers,or may be implemented in a single computing device.

Although an example processing system has been described in FIG. 11 ,embodiments of the subject matter, functional operations and processesdescribed in this specification can be implemented in other types ofdigital electronic circuitry, in tangibly-embodied computer software orfirmware, in computer hardware, including the structures disclosed inthis specification and their structural equivalents, or in combinationsof one or more of them. Embodiments of the subject matter described inthis specification can be implemented as one or more computer programs,i.e., one or more modules of computer program instructions encoded on atangible nonvolatile program carrier for execution by, or to control theoperation of, data processing apparatus. Alternatively or in addition,the program instructions can be encoded on an artificially generatedpropagated signal, e.g., a machine-generated electrical, optical, orelectromagnetic signal that is generated to encode information fortransmission to suitable receiver apparatus for execution by a dataprocessing apparatus. The computer storage medium can be amachine-readable storage device, a machine-readable storage substrate, arandom or serial access memory device, or a combination of one or moreof them.

The term “system” may encompass all kinds of apparatus, devices, andmachines for processing data, including by way of example a programmableprocessor, a computer, or multiple processors or computers. A processingsystem may include special purpose logic circuitry, e.g., an FPGA (fieldprogrammable gate array) or an ASIC (application specific integratedcircuit). A processing system may include, in addition to hardware, codethat creates an execution environment for the computer program inquestion, e.g., code that constitutes processor firmware, a protocolstack, a database management system, an operating system, or acombination of one or more of them.

A computer program (which may also be referred to or described as aprogram, software, a software application, a module, a software module,a script, or code) can be written in any form of programming language,including compiled or interpreted languages, or declarative orprocedural languages, and it can be deployed in any form, including as astandalone program or as a module, component, subroutine, or other unitsuitable for use in a computing environment. A computer program may, butneed not, correspond to a file in a file system. A program can be storedin a portion of a file that holds other programs or data (e.g., one ormore scripts stored in a markup language document), in a single filededicated to the program in question, or in multiple coordinated files(e.g., files that store one or more modules, sub programs, or portionsof code). A computer program can be deployed to be executed on onecomputer or on multiple computers that are located at one site ordistributed across multiple sites and interconnected by a communicationnetwork.

The processes and logic flows described in this specification can beperformed by one or more programmable computers executing one or morecomputer programs to perform functions by operating on input data andgenerating output. The processes and logic flows can also be performedby, and apparatus can also be implemented as, special purpose logiccircuitry, e.g., an FPGA (field programmable gate array) or an ASIC(application specific integrated circuit).

Computers suitable for the execution of a computer program can include,by way of example, general or special purpose microprocessors or both,or any other kind of central processing unit. Generally, a centralprocessing unit will receive instructions and data from a read-onlymemory or a random access memory or both. A computer generally includesa central processing unit for performing or executing instructions andone or more memory devices for storing instructions and data. Generally,a computer will also include, or be operatively coupled to receive datafrom or transfer data to, or both, one or more mass storage devices forstoring data, e.g., magnetic, magneto optical disks, or optical disks.However, a computer need not have such devices.

Computer readable media suitable for storing computer programinstructions and data include all forms of nonvolatile memory, media andmemory devices, including by way of example semiconductor memorydevices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks,e.g., internal hard disks or removable disks; magneto optical disks; andCD-ROM and DVD-ROM disks. The processor and the memory can besupplemented by, or incorporated in, special purpose logic circuitry.

Embodiments of the subject matter described in this specification can beimplemented in a computing system that includes a back end component,e.g., as a data server, or that includes a middleware component, e.g.,an application server, or that includes a front end component, e.g., aclient computer having a graphical user interface or a Web browserthrough which a user can interact with an implementation of the subjectmatter described in this specification, or any combination of one ormore such back end, middleware, or front end components. The componentsof the system can be interconnected by any form or medium of digitaldata communication, e.g., a communication network. Examples ofcommunication networks include a local area network (“LAN”) and a widearea network (“WAN”), e.g., the Internet.

The computing system can include clients and servers. A client andserver are generally remote from each other and typically interactthrough a communication network. The relationship of client and serverarises by virtue of computer programs running on the respectivecomputers and having a client-server relationship to each other.

While this specification contains many specific implementation details,these should not be construed as limitations on the scope of what may beclaimed, but rather as descriptions of features that may be specific toparticular embodiments. Certain features that are described in thisspecification in the context of separate embodiments can also beimplemented in combination in a single embodiment. Conversely, variousfeatures that are described in the context of a single embodiment canalso be implemented in multiple embodiments separately or in anysuitable sub-combination. Moreover, although features may be describedabove as acting in certain combinations and even initially claimed assuch, one or more features from a claimed combination can in some casesbe excised from the combination, and the claimed combination may bedirected to a sub-combination or variation of a sub-combination.

Similarly, while operations are depicted in the drawings in a particularorder, this should not be understood as requiring that such operationsbe performed in the particular order shown or in sequential order, orthat all illustrated operations be performed, to achieve desirableresults. In certain circumstances, multitasking and parallel processingmay be advantageous. Moreover, the separation of various systemcomponents in the embodiments described above should not be understoodas requiring such separation in all embodiments, and it should beunderstood that the described program components and systems cangenerally be integrated together in a single software product orpackaged into multiple software products.

Particular embodiments of the subject matter have been described. Otherembodiments are within the scope of the following claims. For example,the actions recited in the claims can be performed in a different orderand still achieve desirable results. As one example, the processesdepicted in the accompanying figures do not necessarily require theparticular order shown, or sequential order, to achieve desirableresults. In certain implementations, multitasking and parallelprocessing may be advantageous. Other steps or stages may be provided,or steps or stages may be eliminated, from the described processes.Accordingly, other implementations are within the scope of the followingclaims.

Terminology

The phraseology and terminology used herein is for the purpose ofdescription and should not be regarded as limiting.

The term “approximately”, the phrase “approximately equal to”, and othersimilar phrases, as used in the specification and the claims (e.g., “Xhas a value of approximately Y” or “X is approximately equal to Y”),should be understood to mean that one value (X) is within apredetermined range of another value (Y). The predetermined range may beplus or minus 20%, 10%, 5%, 3%, 1%, 0.1%, or less than 0.1%, unlessotherwise indicated.

The indefinite articles “a” and “an,” as used in the specification andin the claims, unless clearly indicated to the contrary, should beunderstood to mean “at least one.” The phrase “and/or,” as used in thespecification and in the claims, should be understood to mean “either orboth” of the elements so conjoined, i.e., elements that areconjunctively present in some cases and disjunctively present in othercases. Multiple elements listed with “and/or” should be construed in thesame fashion, i.e., “one or more” of the elements so conjoined. Otherelements may optionally be present other than the elements specificallyidentified by the “and/or” clause, whether related or unrelated to thoseelements specifically identified. Thus, as a non-limiting example, areference to “A and/or B”, when used in conjunction with open-endedlanguage such as “comprising” can refer, in one embodiment, to A only(optionally including elements other than B); in another embodiment, toB only (optionally including elements other than A); in yet anotherembodiment, to both A and B (optionally including other elements); etc.

As used in the specification and in the claims, “or” should beunderstood to have the same meaning as “and/or” as defined above. Forexample, when separating items in a list, “or” or “and/or” shall beinterpreted as being inclusive, i.e., the inclusion of at least one, butalso including more than one, of a number or list of elements, and,optionally, additional unlisted items. Only terms clearly indicated tothe contrary, such as “only one of or “exactly one of,” or, when used inthe claims, “consisting of,” will refer to the inclusion of exactly oneelement of a number or list of elements. In general, the term “or” asused shall only be interpreted as indicating exclusive alternatives(i.e. “one or the other but not both”) when preceded by terms ofexclusivity, such as “either,” “one of,” “only one of,” or “exactly oneof.” “Consisting essentially of,” when used in the claims, shall haveits ordinary meaning as used in the field of patent law.

As used in the specification and in the claims, the phrase “at leastone,” in reference to a list of one or more elements, should beunderstood to mean at least one element selected from any one or more ofthe elements in the list of elements, but not necessarily including atleast one of each and every element specifically listed within the listof elements and not excluding any combinations of elements in the listof elements. This definition also allows that elements may optionally bepresent other than the elements specifically identified within the listof elements to which the phrase “at least one” refers, whether relatedor unrelated to those elements specifically identified. Thus, as anon-limiting example, “at least one of A and B” (or, equivalently, “atleast one of A or B,” or, equivalently “at least one of A and/or B”) canrefer, in one embodiment, to at least one, optionally including morethan one, A, with no B present (and optionally including elements otherthan B); in another embodiment, to at least one, optionally includingmore than one, B, with no A present (and optionally including elementsother than A); in yet another embodiment, to at least one, optionallyincluding more than one, A, and at least one, optionally including morethan one, B (and optionally including other elements); etc.

The use of “including,” “comprising,” “having,” “containing,”“involving,” and variations thereof, is meant to encompass the itemslisted thereafter and additional items.

Use of ordinal terms such as “first,” “second,” “third,” etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed. Ordinal termsare used merely as labels to distinguish one claim element having acertain name from another element having a same name (but for use of theordinal term), to distinguish the claim elements.

What is claimed is:
 1. A method for operating an inverter-rectifier of abidirectional wireless power transmitter, the method comprising:determining a power flow direction of the bidirectional wireless powertransmitter; controlling, in response to a determination that the powerflow direction is a first power flow direction, the inverter-rectifierto operate in a rectifier mode; generating, during the rectifier mode, azero-crossing signal representing one or more zero-crossings of acurrent at an input of the inverter-rectifier, wherein rising edges ofthe zero-crossing signal indicate zero-crossings corresponding to a risein the current and falling edges of the zero-crossing signal indicatezero-crossings corresponding to a fall in the current; determining,during the rectifier mode, a first delay time based on at least onebidirectional wireless power transmitter parameter and the zero-crossingsignal; generating, during the rectifier mode, first and second controlsignals for first and second switches of the inverter-rectifier,respectively, based on the first delay time and the rising and fallingedges of the zero-crossing signal; and providing, during the rectifiermode, the first and second control signals to the first and secondswitches, respectively.
 2. The method of claim 1, further comprising:inserting, during the rectifier mode, a first dead time between thefirst control signal and the second control signal.
 3. The method ofclaim 1 further comprising: determining a second delay time based on thewireless power system parameter and the zero-crossing signal; generatingthird and fourth control signals for third and fourth switches of theinverter-rectifier, respectively, based on the second delay time and therising and falling edges of the zero-crossing signal; and providing thethird and fourth control signals to the third and fourth switches,respectively.
 4. The method of claim 3, further comprising: inserting,during the rectifier mode, a second dead time between the third controlsignal and the fourth control signal.
 5. The method of claim 3 whereinthe third and fourth switches are coupled to the first and secondswitches in a full-bridge configuration.
 6. The method of claim 1,wherein the first and second switches are operated to provide DC powerto a voltage bus of the bidirectional wireless power transmitter duringthe rectifier mode, the voltage bus being configured to provide thereceived DC power to one of a power source or a load.
 7. The method ofclaim 1, further comprising: controlling, in response to a determinationthat the power flow direction is a second power flow direction, theinverter-rectifier to operate in an inverter mode.
 8. The method ofclaim 7, wherein the first and second switches are operated to provideAC power to at least one coil of the bidirectional wireless powertransmitter during the inverter mode.
 9. The method of claim 1, whereindetermining the power flow direction of the bidirectional wireless powertransmitter includes receiving an indication of the power flow directionfrom a controller of the bidirectional wireless power transmitter. 10.The method of claim 1, wherein determining the power flow direction ofthe bidirectional wireless power transmitter includes receiving anindication of the power flow direction from a wireless power receiver.11. An inverter-rectifier of a bidirectional wireless power transmitter,the inverter-rectifier comprising: a first switch and a second switchcoupled to at least one coil of the bidirectional wireless powertransmitter; and a control system coupled to each of the first switchand the second switch, the control system configured to: determine apower flow direction of the bidirectional wireless power transmitter;control, in response to a determination that the power flow direction isa first power flow direction, the inverter-rectifier to operate in arectifier mode; generate, during the rectifier mode, a zero-crossingsignal representing one or more zero-crossings of a current at an inputof the inverter-rectifier, wherein rising edges of the zero-crossingsignal indicate zero-crossings corresponding to a rise in the currentand falling edges of the zero-crossing signal indicate zero-crossingscorresponding to a fall in the current; determine, during the rectifiermode, a first delay time based on at least one bidirectional wirelesspower transmitter parameter and the zero-crossing signal; generate,during the rectifier mode, first and second control signals for firstand second switches of the inverter-rectifier, respectively, based onthe first delay time and the rising and falling edges of thezero-crossing signal; and provide, during the rectifier mode, the firstand second control signals to the first and second switches,respectively.
 12. The inverter-rectifier of claim 11, wherein thecontrol system is further configured to: insert, during the rectifiermode, a first dead time between the first control signal and the secondcontrol signal.
 13. The inverter-rectifier of claim 11, wherein thecontrol system is further configured to: determine a second delay timebased on the wireless power system parameter and the zero-crossingsignal; generate third and fourth control signals for third and fourthswitches of the inverter-rectifier, respectively, based on the seconddelay time and the rising and falling edges of the zero-crossing signal;and provide the third and fourth control signals to the third and fourthswitches, respectively.
 14. The inverter-rectifier of claim 11, whereinthe control system is further configured to: insert, during therectifier mode, a second dead time between the third control signal andthe fourth control signal.
 15. The inverter-rectifier of claim 11,wherein the third and fourth switches are coupled to the first andsecond switches in a full-bridge configuration.
 16. Theinverter-rectifier of claim 11, wherein the first and second switchesare operated to provide DC power to a voltage bus of the of thebidirectional wireless power transmitter during the rectifier mode, thevoltage bus being configured to provide the received DC power to one ofa power source or a load.
 17. The inverter-rectifier of claim 11,further comprising: control, in response to a determination that thepower flow direction is a second power flow direction, theinverter-rectifier to operate in an inverter mode.
 18. Theinverter-rectifier of claim 17, wherein the first and second switchesare operated to provide AC power to the at least one coil during theinverter mode.
 19. The inverter-rectifier of claim 11, whereindetermining the power flow direction of the bidirectional wireless powertransmitter includes receiving an indication of the power flow directionfrom a controller that is external to the control system of theinverter-rectifier.
 20. The inverter-rectifier of claim 11, whereindetermining the power flow direction of the bidirectional wireless powertransmitter includes receiving an indication of the power flow directionfrom a wireless power receiver.